If you told me before I left on vacation two weeks ago that when I returned Senator Bernie Sanders would have secured huge Democratic platform concessions—a commitment to a $15-an-hour minimum wage, a death-penalty ban, a financial-transaction tax, a modernized version of “Glass-Steagall” banking regulations, a surtax on multimillionaires, Social Security expansion, among other priorities—I’d have expected to see Sanders out campaigning with Clinton this week, having enthusiastically endorsed her.

Instead, Clinton campaigned with progressive icon Elizabeth Warren on Monday, while Sanders continues to say he’ll withhold his support until the Democratic National Committee grants him even more platform wins. My Sanders supporter friends have told me, over the last two months, that their candidate has to hold out to secure the best platform when the party gets to Philadelphia. That may have been true until the last week. But I think Sanders risks weakening his negotiating position by delaying to endorse Clinton, while insisting she and the party accept his every campaign plank, including a single-payer health-care system, a fracking ban, and an aggressive promise by Democrats not to vote for the Trans-Pacific Partnership. (Clinton, like Sanders, opposes the TPP, as do the majority of the DNC platform committee. But the committee voted not to demand a no vote on the trade deal, in order to avoid embarrassing Obama, who is still pushing Congress to approve the TPP.)

Clearly, Sanders’s influence on the platform, and the party, has already been huge. “It would be great if he would just take yes for an answer,” says one pro-Clinton Democrat close to the platform committee. Representative Keith Ellison, a Sanders appointee to the committee, released a statement praising the draft as “the most progressive party platform in years,” while saying he would continue to fight to toughen its language on TPP and the $15-an-hour minimum wage.

“Look, we asked for things that have never been in any platform before,” Ellison told me. “We got Glass-Steagall in there. The death-penalty ban. Four years ago I was running around [the Democratic convention in] Charlotte in a green Robin Hood hat, talking about a fringy weirdo idea of a financial-transaction tax—and we got a financial-transaction tax!” Ellison says he’ll keep pushing his priorities in Orlando, but he thinks progressive Democrats should be proud. “We got a lot of things through.”

So why isn’t Sanders boasting about his platform wins—and taking steps to endorse Clinton, and bring his voters on board? On Sunday he told CNN’s Jake Tapper that Clinton has to make more concessions. “We have made some good gains. We have more to do,” he said. Where Ellison was ebullient about the platform process, Sanders looked dour. He told Tapper: “I think, right now, what we are doing is trying to say to the Clinton campaign: ‘Stand up, be bolder than you have been,’ and then many of those voters in fact may come on board.”

But what more can Sanders realistically expect to win, through the platform process, by withholding his endorsement? The platform will not contain a commitment to single-payer health care. One of the committee’s most ferocious backers of building on the Affordable Care Act, not trashing it, happened to be Sanders’s frequent progressive ally Representative Barbara Lee. She clashed with diehard Sanders backer National Nurses Union executive director RoseAnn DeMoro over why Sanders supporters were diminishing the accomplishment that was the ACA, and not doing anything to enhance it on the road to single-payer, which Lee herself supports (as do I).

“I have to say today that Democrats fought very hard for single-payer and public option. Now close to 20 million have health care now as a result of the Affordable Care Act. That’s a big deal,” Lee told DeMoro. “I just want to make sure that the people who are covered by the Affordable Care Act have your support and you fight for them too.”

The existing platform draft includes a call to build in a public option, including buying into Medicare, into the ACA exchanges in all 50 states. No, it’s not single-payer, but many single-payer advocates seized on the public option back in 2008 as a way to model a form of single-payer that could, if it performs well, provide a bridge to a more fully publicly provided program. But Republicans and conservative Democrats forced the provision from the ACA. The platform commits Democrats to winning it back, which Clinton supports, too.

The platform draft also expresses concern about trade deals, including the Trans-Pacific Partnership, and spells out the negative impact on wages and labor rights such deals have had. It notes that many Democrats oppose the TPP because “the agreement does not meet the standards set out in this platform,” according to a statement from Clinton policy adviser Maya Harris. But it stopped short of insisting that Democrats must vote down the TPP, reportedly because of Clinton-appointed members’ concerns that the party not humiliate President Obama by flatly rejecting one of his remaining priorities at his last convention.

On the one hand, it makes sense that a candidate who is looking to mobilize the so-called Obama coalition does not want to insult its leader. But Ellison thinks the platform can still get stronger on that issue. “As much as I respect President Obama, and I was an early supporter, I am against the TPP. This thing will hurt working people.”

Sanders appointees likewise continue to say that while the platform does include a call to raise the minimum wage to $15 an hour, the language is “vague and insufficient,” in the words of Ellison. He pushed to add stronger language, but his amendment failed. That led to the social-media myth prevalent among Sanders supporters that the platform doesn’t commit to the $15 wage. (By the way, the DNC hasn’t helped itself, or Clinton, by failing to release the latest draft of the platform.)

Sanders supporters like Ellison hope to push the full platform committee a little further in Orlando next month. Clinton appointee Neera Tanden, who has worked for the former first lady, senator, and secretary of state, says there could possibly be more movement, but also suggests that the Clinton side has moved pretty far already. “The platform represents a good-faith effort—more than good faith, really—to accommodate many of Senator Sanders’s ideas,” Tanden says. She adds, a little ironically: “But we also thought it appropriate to make sure it represents some of Secretary Clinton’s ideas, where they differ, because, well, she won the primary.”

And that’s the bottom line. She won the primary. Handily. By three times the number of delegates Obama won by in 2008. Sanders got five platform committee delegates; she got six. There was always going to be negotiation, and he was always going to lose on some issues. Because he lost. Or to put it another way: He failed to marshal a majority of Democratic voters behind his platform.

Of course, Sanders and his supporters can continue to fight for their planks, with the full platform committee in Orlando, and even on the convention floor in Philadelphia. That’s happened before; it hasn’t destroyed the party. What will be destructive, however, is if Sanders continues to tie his endorsement to Clinton’s accepting his remaining platform demands. She can’t, and she won’t. Sanders may even be setting himself up for less influence in Philadelphia, rather than more, with this ongoing crusade. There are certainly progressive Clinton delegates who might want to vote to strengthen the minimum-wage language, or oppose the TPP, to put the party on record behind more progressive goals. But if Sanders is holding Clinton hostage to winning on those issues, not one Clinton delegate will consider anything he’s asking.

Ellison thinks the Clinton side is being a little bit alarmist. “We are all getting there. The fact that Bernie has his fingerprints on the platform in a meaningful way is part of the healing process.” Sanders delegates may push some platform demands even in Philadelphia, Ellison says, but “everybody is going to come together. Bernie is clearly going to be campaigning with Hillary Clinton to defeat Donald Trump. We are all committed to seeing the Democratic nominee, who is Hillary Clinton, win in November.”

Has Ellison endorsed Clinton himself? He chuckles. “I walked right up to her recently and congratulated her and said I will be honored to campaign for her. But I haven’t used the ‘E’ word.” He thinks there’s a downside to Sanders and his surrogates’ enthusiastically backing Clinton too soon: that the senator’s younger supporters will feel abandoned, and won’t come along with the nominee in November.

But there are also risks to waiting too long. Senator Elizabeth Warren has already emerged as a Sanders stand-in, and she’s doing a great job. Meanwhile, if Clinton is forced to court “Never Trump” Republicans because Sanders delivers a late or halfhearted endorsement, he and his backers will lose some influence politically. There are many Republicans available to Clinton, particularly women, if she decides that’s her best audience. As one Clinton supporter close to the platform negotiations told me: “It’s really up to him: He can determine if she does this with a progressive mandate, one that she has to be loyal to. But if his voters snub her, and she has to go to anti-Trump Republicans to get to 51 percent, they’ll have much less leverage.”